|(Lady Gaga is an excellent source of exaggerated imagery)|
Leonard et al., (2008) recruited 100 men and 100 women and imaged their brains. They showed that men generally have larger brains that women (not surprising, men generally have larger bodies than women).
|Leonard et al., 2008 Figure 2|
But what is fascinating is that when comparing specific regions, the gender of the brain mattered less than the size of the whole brain.
In other words if you had a small male brain, it would look almost indistinguishable from a large female brain. (See their Figure 3)
What I find most interesting in this paper is that it refutes the much purported "Corpus Callosum Myth".
|Corpus Callosum (source)|
The Corpus Callosum is main white matter connection between the two hemispheres of the brain. The "Corpus Callosum Myth" is that female brains have larger corpus callosa than male brains.
I have to admit that I am not immune from gender bias. When I first heard that women had larger corpus callosa than men, my immediate thoughts were towards how that could make sense. I thought "ah, well then maybe that is why women are better at seeing the big picture or at multi-tasking" and other thoughts along those lines.
What I definitely did NOT think was "I bet that was a small, poorly controlled study which did not even reach statistical significance." Well as it turns out, I should have. DeLacoste-Utamsing and Holloway (1982) analyzed only 14 brains (9 male and 5 female), and found that
"The average area of the posterior fifth of the corpus callosum was larger in females than in males (p=0.08)" DeLacoste-Utamsing and Holloway (1982) p. 1431
A result hardly worth speculating upon.
Leonard et al., 2008 also found some corpus callosum differences between the genders, but when they graphed the size of the corpus callosum against the size of the whole brain...
|Figure 3B (female brains white circles, male brains filled squares)|
As with Von Economo neurons, maybe brains of different sizes work similarly, but have to be shaped differently to do so.
So rather than wildly speculating that women are better at this or that because they have stronger connections between their hemispheres, we should put our efforts into discovering evolutionary reasons why small men would be better multi-taskers that large men.
UPDATE (7/23/12): I just want to be perfectly clear. I don't actually think that small men think like women. The whole point of this post is to show that popular studies explaining that 'men and women's brains are different' may sound like they make sense, but there is often another explanation. In this case: if you are going to claim that the size of the corpus callosum means that women are better multi-taskers, then you have to ALSO claim that small men are better multi-taskers. And that large women are worse multi-taskers. (These seem like totally ridiculous claims to me, but feel free to construct an experiment to test these hypotheses).
For more on gender and gender differences (or lack thereof) in the brain, see my previous posts:
Leonard CM, Towler S, Welcome S, Halderman LK, Otto R, Eckert MA, & Chiarello C (2008). Size matters: cerebral volume influences sex differences in neuroanatomy. Cerebral cortex (New York, N.Y. : 1991), 18 (12), 2920-31 PMID: 18440950